There are many types of fluid pressure relief or vent valves known for use with liquid or fluid storage tanks. These tanks may be of the type, for instance, that are transported by truck or rail and which many times are adapted to be transferred aboard a ship at dockside. Many times these tanks contain flammable liquids, and the various governmental regulatory agencies, such as, for instance, the Department of Transportation, or the Coast Guard, require that sufficient venting capacity be provided to take care of expanding vapors in a storage tank in the event of fire. This venting capacity is adapted to prevent the rupture of the tank and may require a venting capacity as high as for instance, 400,000 cubic feet per hour.
So far as I am aware, prior art venting arrangements have not been able to provide a large venting volume utilizing a single device or valve, and still remain within acceptable size limits for the device. Moreover, many prior art venting arrangements are exposed to the elements or weather, and many times are subject to being tampered with, resulting in the possibility of pilferage of the contents of the tank.